1. Field of the Invention
This invention relates to devices for filtering fluids such as lubricating and fuel oils, and more particularly to a filter assembly incorporating a spirally wound roll of tissue paper as a filtering element.
2. Description of the Prior Art
A preliminary patentability and novelty search in Class 210, sub-classes 494.1, 439 and 232 has revealed the existence of the following fourteen U.S. patents:
______________________________________ 2,661,846 2,928,547 3,308,956 3,317,053 3,481,478 3,487,942 3,504,803 3,526,590 3,868,325 3,872,008 3,912,631 3,975,273 4,454,036 2,738,879 ______________________________________
The useful life of an internal combustion engine is directly affected by the cleanliness of the lubricating oil utilized to prevent metal-to-metal contact between relatively moving metal parts. Lubricating oil contaminated with solid particulates such as dirt, sludge, and metal particles serves to transport such contaminants between relatively moving metal parts, where they act as an abrasive to cause premature and excessive wear of the parts.
In connection with oil-type fuels, such as diesel, it is important that entrained solids be filtered from the stream of fuel before the contaminating solids reach the fuel injectors, which might otherwise be clogged by solid contaminants.
In modern internal combustion engines, it is not uncommon for the engine to revolve at 3000 revolutions per minute (RPM) at cruise speeds, with engine RPMs of over 4000 and 5000 not being unusual. At these high RPMs, it is particularly important that the lubricating oil be kept clean and free of solid contaminants because the abrasive effect of the contaminants at these velocities is enhanced, thus causing excessive wear of the engine parts subjected to the abrasive action of the contaminated oil.
Since my initial invention of an oil filter device utilizing a conventional roll of toilet tissue as the filtering element, as illustrated and described in my previous U.S. Pat. No. 2,738,879 issued more than thirty years ago, and my subsequent invention as illustrated and described in U.S. Pat. No. 3,308,956 issued more than twenty years ago, many different structures have been invented, as exemplified by the prior art patents noted above, which utilize a roll of tissue paper as the filtering element. Each is different from the others in some particular novel respect, each attempting by some different mechanical means to solve the problems inherent in the use of a roll of tissue paper as the filtering element. In most instances, the roll of tissue paper is a roll of toilet tissue paper commercially available at a very low cost compared to other manufactured filter elements.
Thus, one of the characteristics of a roll of toilet tissue as a filtering element is that oil will not flow radially through the roll, i.e., transversely through successive plies. Oil will only flow axially through the roll, parallel to the plies. That being the case, since a conventional roll of toilet tissue is wound about an almost universally standard diameter paper core, and possesses a substantially universally standard outside diameter, it is clear that the effective cross-sectional area of the filter element is pre-determined by these factors. Accordingly, one of the important objects of my invention is to utilize a maximum amount of the effective cross-sectional filtering area of the roll while forcing all fluid to pass longitudinally parallel to the plies.
While filtering devices that utilize a roll of toilet tissue as the filtering element have become quite popular, the complaint that is heard most frequently from users is that changing the filter is a messy job. The complaint is not without merit when considered in relation to these type of filter units prior to the invention described herein. The reason lies in the fact that this problem has not heretofore been specifically addressed by manufacturers of the hardware. Accordingly, another object of the invention is the provision of a filter assembly for use with a roll of toilet tissue as a filter element which effectively eliminates the spilling of oil when the filter element is changed.
Through years of experience with engines, oil distribution systems, full-flow filters and by-pass filters such as the one forming the subject matter of the instant invention, I have become aware of many of the problems inherent in lubricating oil filtration systems for internal combustion engines. One of those problems arises from the fact that full-flow filters must be designed in such a manner that they accommodate oil flow even if the oil is dirty. In some full-flow filter assemblies a by-pass valve is included which opens when the filter element becomes clogged. In other full-flow filter assemblies, the construction of the filter element is such that it cannot be clogged. This is usually accomplished by controlling the density of the filter element so that it does not filter out or trap the fine impurities that are suspended in the lubricating oil. Accordingly, still another object of the invention is the provision of a by-pass type filter assembly which cooperates with the conventional oil filter of an internal combustion engine to eliminate from the oil stream the fine impurities that normally pass through conventional full-flow oil filters.
Another complaint frequently heard from users of the old style Frantz by-pass filter utilizing a roll of toilet tissue, such as the structures illustrated in U.S. Pat. Nos. 2,738,879 and 3,308,956, is that the filter element, namely, the roll of toilet tissue, is difficult to remove from the cannister because there is no easy way to grasp the oil-soaked filter unit. Accordingly, a still further object of the invention is the provision of an oil filter assembly in which provision is made to facilitate removal of the expended filter element when it becomes necessary to change the filter element.
At least one by-pass filter assembly on the market is referred to as a "spin-on" type. This means that after a base member is fixed in the engine compartment and appropriate hoses connected to the base member, a filter element permanently enclosed within a metal cannister is "spun on" the base member. To replace the filter element, the entire cannister is removed and discarded and a new cannister with a new filter element enclosed is purchased for about $12 retail and applied to the base member. From my experience, it appears that the $12 cost is prohibitive and constitutes an impediment to the sale of the unit even though it may be very effective in cleaning lubricating oil. Accordingly, a still further object of the invention is the provision of a filter assembly in which only the filter element per se need be changed, where the filter element is a roll of commercially available toilet tissue, and the cost of replacement of the filter element is orders of magnitude less than the cost of replacing the complete cannister.
The invention possesses other objects and features of advantage, some of which, with the foregoing, will be apparent from the following description and the drawings. It is to be understood however that the invention is not limited to the embodiment illustrated and described since it may be embodied in various forms within the scope of the appended claims.